This invention relates to a draw frame for processing a fiber bundle composed of a plurality of slivers. The draw frame includes a creel, a measuring assembly and a draw unit. The slivers are introduced from the creel to the draw unit, then run therethrough while a measuring assembly disposed between the creel and the draw unit senses the thickness of the slivers. The measuring signals of the thickness sensor are used for regulating the draw frame. A sliver guide and a sliver trumpet are positioned downstream of the draw unit as viewed in the direction of sliver run.
The coiler cans containing the sliver to be introduced into the draw frame are conventionally arranged along one side or both sides of the creel. Above each coiler can a withdrawing device is arranged by means of which the sliver is pulled from the respective coiler can and is deflected in the direction of the draw frame. The slivers are advanced above the creel and are subsequently combined into a fiber bundle. The fiber bundle which is thus composed of a plurality of slivers is admitted into the draw unit after it passes a sensor. In the draw unit the slivers are stretched and doubled and are subsequently gathered in a sliver guide arranged at the outlet of the draw unit and then introduced into a sliver trumpet and combined into a single, stretched sliver for subsequent processing.
As described in German Offenlegungsschrift (application published without examination) 42 12 720, a storage belt is provided on which piles of slivers are positioned at several storage emplacements. Above the storage belt a conveyor belt is positioned which advances the slivers to the draw frame. Above each emplacement a pressing roll cooperates with the conveyor belt. The pressing rolls are preceded by deflecting guides which orient the sliver, taken from the emplacement, to the wedge-shaped gap provided between the pressing roll and the conveyor belt. The sliver removing device is essentially formed by the pressing rollers and the deflecting guides. Immediately upstream of the draw frame a driven deflecting roller cooperates with the conveyor belt. Further, immediately upstream of the draw frame a funnel-shaped densifier is provided which gathers the incoming slivers into a densified sliver bundle. An intake roll pair of the draw frame subsequently advances the sliver bundle to a roll pair which, as a measuring member, monitors the mass of the throughgoing sliver bundle by performing a mechanical mass measurement (thickness measurement). This is effected by passing the sufficiently densified sliver bundle through an intake funnel under a highly loaded floating pressure roll whose excursions are detected. Such excursions which represent the mass (thickness) variations of the sliver bundle, are converted into electric signals which, in turn, are used to regulate the draw unit. The drawn sliver discharged from the draw frame is deposited into a coiler can.
It is a disadvantage of the above-discussed conventional system that the fiber material is caused to change its running direction repeatedly from the time it is positioned on the conveyor belt until it is pulled off by the output rolls situated downstream of the draw unit of the draw frame. Each change of direction requires suitable structural elements and each such change involves frictional losses.
It is a further disadvantage that the configuration of the fiber material changes several times: in one phase it is advanced as separately running slivers and in another as a compressed sliver bundle which is then separated into individual slivers. These eventually emerge as the final, single, drawn output sliver. Thus, in the region of the draw unit the slivers are pressed between a pressure roll and a lower roll into a sliver bundle which, as known, subsequently again spreads into individual slivers and runs in this condition through the draw unit. At the output of the draw unit a sliver guide laterally gathers the individual slivers and combines them into the final output sliver. This procedure imparts to the slivers undesired structural changes, in addition to the earlier-noted directional changes.
It is yet another disadvantage of the conventional apparatus that it is of complex and expensive construction. Also, the multiple directional and shape changes adversely affect the output rate.